#1684 slightly varied RF startup time and, as a result, threw ContikiMAC timing configuration off. This manifests itself with very poor CC13xx PROP mode radio performance, as documented in #1747.
This pull fixes this bug by slightly increasing ContikiMAC's inter-packet interval. This gives the receiver a little more time to respond with an ACK to unicast frames.
Fixes#1747
`CC2650_FAST_RADIO_STARTUP` is required for TSCH, but it currently breaks ContikiMAC. We set the default value to the one that will work with the default choice of RDC.
Fixes#1744
According to the CC1310LP design files, the flash on it is the same as the flash on the CC2650 LP (MX25R8035F 8Mbit). However, the flash on some CC1310 LPs reportedly identifies itself as the 16Mbit one (MX25R1635F). Instruction sets are identical, we simply need to tell the driver to recognise this part's Device ID.
The block that controls the `.upload` target is unnecessarily replicated in multiple sub-board Makefiles. This was originally done because the SmartRF and the Launchpad can be programmed with the c2538-bsl script, whereas the sensortag cannot.
This commit moves the `cc2538-bsl` / `.upload` target logic to the top level cpu Makefile (`cpu/cc26xx-cc13xx/Makefile.cc26xx-cc13xx`). Board makefiles simply set the make variable `BOARD_SUPPORTS_BSL` to 1 to signal that they can be programmed by the BSL script. If `BOARD_SUPPORTS_BSL` is not equal to 1, trying to use the `.upload` target will return an error message.
For example:
```
$ make BOARD=sensortag/cc2650 cc26xx-demo.upload
using saved target 'srf06-cc26xx'
This board cannot be programmed with the ROM bootloader and therefore does not support the .upload target.
```
This commit creates a `common` directory, aimed to host drivers supported by multiple boards of the CC13xx/CC26xx family.
We move the Sensortag SPI and External Flash drivers to this location and we change the Sensortag build system to pull the respective files from therein.
The driver currently supports two Winbond external flash parts with identical instruction sets. The instruction set of the Macronix MX25R8035F appears to be a superset. We therefore change the driver to add the MID/DID of the Macronix to the list of supported parts.
This will subsequently allow us to share the same driver for both the SensorTag and the CC2650 LauchPad.
